Assessment of Depressive Symptoms During Inpatient Rehabilitation for Spinal Cord Injury: Is There an Underlying Somatic Factor When Using the PHQ?

Objective: To test the hypothesis that a 2-factor solution, including a somatic factor, best accounts for the response pattern to the Patient Health Questionnaire-9 (PHQ-9) during inpatient rehabilitation after spinal cord injury (SCI). Research Design: 568 adults with traumatic SCI were administered the PHQ-9 during inpatient rehabilitation. The PHQ-9 was developed to identify depressive disorders based on DSM-IV criteria. Results: Maximum likelihood confirmatory factor analysis was used to compare unidimensional and alternative 2-factor models. The results suggested that the 2-factor solution with 3 somatic items (sleep disturbance, poor energy, appetite change) was a better solution than either a unidimensional model or 2-factor model that included psychomotor retardation as a fourth somatic item. The root mean square error of approximation with 3 somatic items fell within the acceptable range of less than .08 (.073). The 2 factors were highly correlated (.76) but within the acceptable range (less than .80). Conclusions: There may be 2 underlying factors with the PHQ-9, including a somatic factor, when measuring depressive symptoms during inpatient rehabilitation for SCI.